| Due to quantum confinement effect,colloidal semiconductor nanomaterials have excellent optoelectronic properties.Therefore,they are of great value in application in the fields of photodetection,backlight display,and microcavity lasers.Thick-shell QDs have efficient photoluminescence（PL）properties benefiting from the effective isolation of surface defects.The semiconductor carrier dynamic can be controlled utilizing the interaction with confined electromagnetic modes in a microcavity,and many new physical phenomena have emerged due to the coupling of excitons and photons.In this thesis,multiexciton dynamics,optical gain properties and the effects of charged states on non-radiative Auger recombination in thick-shell core/shell QDs are investigated,and their application in microcavity lasers is explored.In addition,the exciton-polariton is constructed a high-Q factor dielectric microcavity with 2D nanoplatelets（NPLs）.The polariton condensation is realized for the first time in this system.The main research contents are organized as follows:A series of green emitting Cd Zn Se S/Zn S gradient-alloy core/shell QDs with controlled shell thickness were synthesized.The influence of shell epitaxy on the biexciton Auger recombination is analyzed by PL lifetime,single-dot PL trajectories and biexciton decay traces.The conclusion is that the shell thickness of 3 monolayers have the most excellent properties benefiting from well passivation of surface defects,graded alloy interface and moderate compressive stress during epitaxy,such as PL quantum yield up-to 85%,suppressed blinking,long biexciton Auger lifetime of 400 ps,and amplified spontaneous emission（ASE）threshold of 106.7μJ cm-2.A vertical-cavity surface-emitting laser was fabricated by utilizing such QDs considering the low-threshold optical gain property,and bright multi-mode laser emission was obtained.The thick-shell Cd Se/Cd Zn S/Zn S QDs with gradient alloy interface was synthesized and the dynamic of neutral/charged biexciton dynamics were investigated.An ultrafast emission in the high energy shoulder of to band-edge luminescence was observed in the transisient PL spectra,which corresponded to the 1P transition of the Cd Se core.The redshift and band-edge emission rate acceleration were attributed to the increased Coulomb interaction accompanied by the intrinsic Stark effect and enhanced dielectric screening effect of charged biexciton,which result in a larger binding energy and opening of additional Auger recombination channels.The QDs film exhibits a low-threshold(81μJ cm-2)stable optical gain.Based on these,a single-mode emission vertical cavity surface emitting laser is fabricated.The PL decay curves in the microcavity and free space were compared,which proves the exciton spontaneous emission rate was accelerated by 5.74 time owing to the Purcell effect.The microcavity emission property was analyzed with the traditional microcavity rate function.A Fabry-Pérot microcavity consisted of 2D Cd Se/Cd S NPLs were fabricated and the microcavity dispersion property was measured by home-build angle-resolved PL/reflectivity spectra.The strong coupling of NPLs exciton and microcavity photon was confirmed and a large Rabi splitting energy of 76 me V was obtained.Under femtosecond laser excitations,the NPLs microcavity exhibits polariton Bose-Einstein condensation and polariton lasing above a threshold of 0.5μJ cm-2.This conclusion is further strengthened by a super-linear pump-power-dependent ground state emission,macroscopic ground-state occupation,the full wavelength at half maximum（FWHM）narrowing,blueshift of the ground-state emission and the build-up of long-range spatial and long temporal coherence.The dynamic measurement confirmed the stimulated scattering of polaritons resulted in polariton condensation. |
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